Range finder



July 4,V 1939.. E. MATHER RANGE FINDER Filed Aug. 19. 1937 lvmlul A3 4s lols Patented July 4,1939

A Ulu'rizo STATES PATENT orifice My invention ,relates generally to` range nders, of simple and economical construction usable by amateur and professional photog-v raphers accurately to gauge distances.

In photography, it is important to know quite accurately the distance between'the object to be photographed and the lens of the camera so that the camera may be-properly focused upon the object. Various types of meters and. range nders for thispurpose have been proposed and used, but in general the instrumentslcomprise l lenses, mirrors, and adjusting devices which not only are rather difficult to use'but are necessarily of such high'cost as to' be unsalable to the aver- I age amateur photographer.

It is thusthe object of my invention to provide a greatly simpliiied, relatively cheap' range finder by which distances may be determined with an accuracy comparable with that of the focusing apparatus of the ordinary camera.

A further object is to provide a photographic range finder which is` very compact and which is simple and easy to operate.

Other objects will appear from the following description, reference being had to the accompanying drawing, in which:

Fig. 1 is a perspective View showing the manner of` using the range inder; 1

Fig. 2 is a geometrical diagram to illustrate the theory'of my improved range finder;

Fig. 3 is a'front elevation of the range finder;

Fig. 4 is a transverse sectional view taken on the line 4 4 of Fig'. 3;

Fig. 5 is a longitudinal sectional view taken l on the line 5 5 of Fig. 4;

Fig. 6 is a front elevation of a of my invention; and

Fig. 7 is a longitudinal sectional view of the modified form of Fig. 5, taken just' inside `the front sheet.

modified form The range finder of my invention operates upon the principle that ,in .looking at an object, the angle of which the object is the apex and s which is subtended by the interpupilary distance, is a measure of the distance between the `observer and the object. l'I'hus in Fig. 2, A and B represent the left and right eyes v.respectively of an observer focused upon an object O. If a suitable scale is now interposed between the observer and the object, `the line of sight A O of the' left eye will intersect the scale at the point C, and that of the right eye will intersect the vscale at D. If the distance a between the scale and the eyes of the observer is known, the interpupilary distance c known, and the distance b between C and D determined, the 4distance d between theobserver and the object may easily be computed by the formula: d==ca/(cb).

The range nder, as bestshown in Figs. 3, 4, and 5, comprises a front -sheet vIII cemented or otherwise secured to a rear sheet I2 by means of intermediate spacing strips' I4 and I5, these parts forming a guide for a slidev I6. All o1 these partsv may be made of Celluloid, Bristol board, cardboard, a moulded sheet plastic, or any other similar material, preferably one which may be easily cut and formed and which will form a suitable base upon which indicia Vmay be printed.

The front sheetv I0 is provided with .a square aperture I8, through which a sight projection 20 formed from the rear sheet I2 is visible. The frontsheet III also has an elongated generally rectangular 'opening 22 formed therein, through which the upper portion of slide I6 is visible, A notch 24 is formed at' the right hand (Fig. 3) end of the front sheet I0, the notch being formed to provide a pointer 26 cooperable with a sca1e28 printed or otherwise marked upon the slide I6.

The slide I6 isconformed to slide freely between'the sheets I0 and I2,its movement being limited by a tape 30 which passes through slots 32, 33 formed in the front sheet I0 and corresponding slots 34, 35 -formed in the rear sheet.

I2, and extends through an elongated slot 36 in the slide I 6. The slide- II has a sight-opening 38, the opening having sight projection 40. The slide is provided with a tab 42 which projects beyond the` right hand ends of the sheets IIJ and I2 when the slide is moved to its innermost position. V Y

The ribbon or tape 30 is Vpreferably provided with suitable buckle devices 44 by which its length may be adjusted to compensate for variations in the interpupilary distances of the users.

The range Afinder is use d in the manner illustrated in Fig. 1. The range ilnder is held between the eyes of the user and the object the range of which-is to be ascertained with the ribbon or tape around the neck of the user and ldetermining the distance of the range nder from his eyes. With the eyes focused upon the object, the left eye sights the object by looking through the opening I8 andvmoving the finder until the point o1'- the sighting projection v2li appears to rest upon some selected point on the object. The slide I6 is then moved until its sighting projection is in the line of sight of the right eye and the selected point on the object. In practice the slide is moved until the'sighting projections 20 and 40 appear to be in exact vertical alignment with each other. Under these conditions, the pointer 26 in cooperation with the scale 28 will indicate the number of feet the object is distant from the eyes of the observer.

If the user has difculty in keeping his eyes focused upon the distant object while adjusting the position of the slide, he may in rapid alternation sight the object with his left eye through aperture I8, keeping his right eye closed, and sight the object with his right eye through aperture 38, keeping his left eye closed. When using the range finder in this manner, it is, of course,

very important that the user does not move the range nder or shift his head between alternate sighting operations.

The modification shown in Figs. 6 and 7 comprises front sheet 50 and rear sheet 52, cemented or otherwise suitably secured to separating blocks 54, 56, 51 and strip 58. The sheets 50, 52 are thus spaced'to receive a slide 60. The slide 60 has elongated slots 62, 63 embracing the blocks 56, 51 respectively, and a slot 64 to permit movement of the slide with respect to a tape 66 which may be secured to the nder in the manner illustrated in Fig. 7 or in the manner previously described with reference to the structure of Figs. 1, 3, 4, and 5. The slide has a rectangu. lar sighting notch 66, while the front and rear sheets 50, 52 have similar registering sighting notches 68 and 6!! respectively.

The slide 68 is cut away at 1 0 so as not to interfere with the line of sight through notches 68, 69, while the front sheet 50 and rear sheet 52 are provided with large rectangular notches 12, 13 respectively, so that lthe user may sight through notch 66 irrespective of the position of the slide 66. The slide 60 has an indicating arrow 14 marked thereon for cooperation with graduations of a scale I6 marked upon the face of sheet 50 at the lower edge of the notch 12.

The range finder of Figs.v 6 and '7 is used in the same manner as previously described with reference to the. embodiment shown in Figs. 1, 3, 4, and 5. Some users iind it easier to sight through the open notches 66, 68 than through apertures I8, 38 of the first described embodiment.

It will be apparent to those skilled in the art that the invention may be embodied in various forms. For example, the front and rear sheets may be made of a single integral sheet folded back upon itself. Other similar variations in construction may be made without departing from the principles of the invention asset forth in the following claims.

1. In a photographic range finder, the combination of a body member having a sight opening, a slide member movable with respect to said body member and provided with a sight opening, means secured to said body member for determining the distance said members shall be held lfrom the eyes of the user, a pointer-on one of said members, and a scale on the other of said members, said scale being graduated to read the distance of an object from the eyes of the user when the user observes said object with the line of sight to one 'eye passing through the si'ght opening of said body-member, and the line of sight to the other between an object and the two' eyes of a user, and

a scale on said means for indicating the setting thereof, said scale being calibrated to show d.- rectly the distance between said object and the eyes of the user. I

3. A range finder comprising a front sheet and a rear sheet, means for securing opposite edges of said sheets together in spaced relation, said sheets having registering elongated slots formed therein, and one of said sheets having a sight projecting into the slot therein, a slide reciprocable in the space-between said sheets, said slide having a sight visible through the slots sheets for determining the distance said sheet shall be held from the eyes of the user.

4. A range nder comprising a front sheet and a rear sheet, means for securing opposite edges of said sheets together in spaced relation, said sheets having registering elongated slots formed therein, and one of said sheets having a sight projecting into the slot therein, a lslide reciprocable in the space between said sheets, said slide having a sight visible through the slots formed in said sheets, cooperative scale means on said slide and one of said sheets, and means secured-to said sheets for determining the distance said sheet shall be held from the eyes of the user.

5. In a photographic r'ange finder, the combination of an elongated sheet having a sighting notch formed in one longitudinal edge thereof, a member slidably mounted with respect to said sheet and having a sighting notch in the edge thereof in longitudinal alignment with the notched edge of said sheet, and means to hold said sheet and slide a determined distance from the eyes of the user.

6. In a photographic range nder, the combi,

nation of an elongated sheet having a sighting notch formed in one longitudinal edge thereof, a member slidably mounted with respect to said sheet and having a sighting notch in the edge .thereof in longitudinal alignment with vthe notched edge of,said sheet, cooperating scale means on said slide and said sheet calibrated to indicatethe distance` between an object and the eyes of the user when the lines of sight between said object and the eyes of the user pass respectively through `said notches, and means to hold said sheet and slide a determined distance from the eyes of the user.

7. A photographic range finer comprising a pair of relatively movable sighting elements, means for determining the distance that said sighting element shall be held from the eyes of the user, and a graduated scale operated by said elements to indicate the distance between an object andthe eyes of a user when the lines of sight from said 'object to the eyes are respectively in line with said sights when the latter are held at said predetermined distancev from the eyes IRWIN E. MATHER.

, formed in said sheets, and means secured to said 

